Rubber composition and method of



Reissued July 23, 1935 UNITED sm'rss PATENT OFFICE RUBBER COMPOSITION AND METHGD F PRESERWNG RUBBER Marion 0. Reed, Lakewood, Ohio, assignor to The B. F. Goodrich Company, New dio ik, N. 3L, a corporation of New York 28 Claims.

'Ihisiinvention relates rtothe art of preserving rubber, either Lin a (vulcanized or unvulc'anized condition, and to rubber compositions s0 iprewtved.

It is well known thatrubber deterioratesmore or less rapidly upon aging, especially when exposed .to light, heat, or air. It has heretofore 'been proposed to retard such deterioration by -.treating the .rubber, either before ,orafter vulcanization, with so-called "anti-oxidants or age-resistors, such as amino compounds, bydroxy compounds, and aldehyde-amine condensation products.

I'Ihe present invention, briefly stated, consists '13 'in.treating rubber with a member of a class of anti-oxidants which has been 'found to be unusually effective in retarding the deterioration of rubber compositions. This class of compounds includes substances possessing the structural l as where C1 and C2 are terminal carbon atoms of a saturated or unsaturated chainLR is an arcrmatic 1 nucleus :directly attached to the nitrogen 30 atom, and X is as. hydroxyL-nitroso, orrafmlno .sgroup.

Preferably C1 and C2. are the terminal carbon atoms of a saturated chainiwhicmmay .or may -not contain other atoms vthan carbon, ,the ':sub-- 35 stituents on the various atoms of the chain, and ,particularlyon the terminal carbon atomsrCnand lCz, if other than hydrogen, preferably being monovalent. radicals whichdo not containdouble 'bonds, such as alkyl, alkoxy,'hydroxy, etc. Sub- 40 stituents containing doubly bound oxygen, ,such as carboxyl and carbonylgroups, tend to'decrease the effectiveness of the compounds as, anti-oxi- 'dants. The groupR mayibe any aromatic nucleus such as'a' benzene or naphthalene nucleus. :45 The activity of the'compound'is'somewhat affected' by the position of the substituent group X. *Forexample, if R is a benzene nucleus, the compouncls containing thesubstituent x 4n the ortho position aremore active than those in which' it s50 occupies the meta. position, .while compoundswin which it takes the para. position are still more motive.

Althoughthe compounds in which thearomaticanuclens is unsubstituted; or contains other c155 substituentsnsuehes aminmor nitroso groups,

p-hr mw; Nrpheerl piner 'iin C H:-C H:

o-hydrory N-phenyl morpholine,

. pm dliitroso-diphenyl piperazine,

C HP C H:

0 N OH p-hydrom N, phenyl morp holine.

s hydro N-nephthyl morpholine,

'GHr-GH:

2 methyl, ihydroxy N-phenyl tetra-hydro l, 4 thiamine,

2, 4 diamino' N phenyl carbazole.

It will be noted that each of these compounds contains an aromatic nucleus (preferably with a hydroxyl, nitroso, or amino group-including secondary and tertiary amino groups-substituted in the para position) attached to the nitrogen of a heterocyclic ring. That is, the nitrogen which is attached to the aromatic nucleus is likewise attached to both ends of a chain of atoms, the nitrogen together with the said chain constituting a heterocyclic nucleus. No explanation has been found for the peculiar relationship of the molecular structure of the compounds to their antioxidant powers, but numerous tests have demonstrated the efficacy of substances possessing this molecular structure.

The substances belonging to the class defined above are extremely effective in retarding the deterioration of rubber. If employed in rubber compositions in the same proportions as most previously known anti-oxidants, they are far more effective, whereas small proportions of these substances are as effective as much larger proportions of previously known substances. They are odorless and do not impart an odor to a vulcanized rubber composition into which they have been incorporated. Many of these substances have practically no effect on the color of rubber, and hence may be employed in white or light colored compositions without fear of darkening or staining.

Example 1.As a specific example of one embodiment of the method of this invention, a typical tire tread composition was prepared containing: blended plantation rubbers 100 parts by weight, sulfur 5.5 parts, zinc oxide parts, gas black parts, mineral rubber 10 parts, palm oil 5 parts, and hexamethylene tetramine 0.75 part. This was divided into five portions, one of which was used as a control. To the others were added respectively 0.47, 0.95, 1.90, and 3.80 parts of phydroxy N-phenyl morpholine 70, 1%, and 2% of the weight of the composition). The compositions were thoroughly mixed, and vulcanized in a press minutes at 145 C. (294 F.) to produce an optimum cure. The relative rates of aging of the vulcanized compositions were compared by measuring their respective tensile strengths and elongations before and after aging. Accelerated aging tests were carried out in the most varied nature.

Aging tests of p-hydrowy n-phenyl morpholine After 48 After 7 days i Before aging in the (leer ig f Proportion of Davis bomb anti-oxidant T E '1 E T E compositions were tested in the manner described in Example 1, after vulcanization for thirty minutes and forty-five minutes at 294 F.

Aging tests of p-nitroso N-phenyl morpholine After 48 hours in the Bierer- Davis bomb 1 After 7 days in the Gear oven Before aging Anti-oxidant None (vulcanized 30 mintes) u 3475 676 1783 527 925 420 p-nitroso N-phe nyl morpholine (vulcanized 30 minutes) 3441 643 2650 565 2191 537 None (vulcanized M minutes 3600 623 1802 457 731 280 p-nitroso N-phenyl morpholine (vulcanized 45 minutes) 3402 580 2590 450 i860 433 It is evident that the rubber vulcanized in the presence of p-nitroso N-phenyl morpholine resists deterioration due to aging to a much greater degree than rubber vulcanized with other accelerators.

Obviously, the practice of this invention is not limited to the specific compositions given above, such compositions being merely illustrative of specific methods of employi'ngfthe anti-oxidants of this invention. The proportions of the constituents may be varied, or other substances may be substituted therefor, since this invention is applicable to pure rubber or rubber compositions of the The anti-oxidants may also be applied to unvulcanized or vulcanized rubber with good efiect on the age-resisting properties of the rubber, such as by applying them to the surface oii the rubber, as for example in solution, or in the form of a paste or emulsion.

It is tobe understood that the term treating as employed in the appended claims is used in a generic sense to include either the incorporation of the anti-oxidants into the rubber by milling or similar process, or their addition to the rubber latex before its coagulation, or to the application thereof to the surface of a mass of crude or vulcanized rubber. The term rubber is likewise employed in the claims in a. generic sense to include caoutchouc, whether natural 'or synthetic, reclaimed rubber, balata, gutta percha,

i rubber isomers and like products, whether or not admixed with fillers, pigments, vulcanizing; or accelerating agents. The term amino group" is herein employed to refer only to compounds in which the basic nitrogen atom is attached by single bonds to hydrogen atoms and/or to carbon atoms which in turn are attached only to further hydrogen or carbon atoms, and therefore excludes such groupings as those of amides and amidines.

While I have herein disclosed certain preferred manners of performing my invention, I do not thereby desire or intend to limit myself solely thereto, for as hitherto stated, the precise proportions of the materials utilized may be varied and other materials having equivalent chemical properties may be employed if desired without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. The method of preserving rubber which comprises treating rubber with a compound possessing the structural formula where 01 and C: are terminal carbon atoms of a chain, R is an aromatic nucleus, and X is a group selected from the class consisting of hydroxyl, nitroso, and amino groups.

2. The method of preserving rubber which comprises treating rubber with a compound possessing the structural formula where C1 and C2 are terminal carbon atoms of a chain containing only monovalent substituents which do not possess double bonds, and R is a p-arylene group.

3. The method of preserving rubber which comprises treating rubber with a compound possessing the structural formula where C1 and C2 are terminal carbon atoms of a saturated 5-membered chain, the atoms constituting the chain containing only monovalent substituents which do not possess double bonds.

4. The method of preserving rubber which comprises treating rubber with p-hydroxy N- phenyl morpholine.

5. A composition of matter comprising rubber and a compound possessing the structural formula '0 I \N-R--X where C1 and C2 are terminal carbon atoms of a chain, R is an aromatic nucleus, and X is a substituent selected from the class consisting of hydroxyl, nitroso, and amino groups.

6. A composition of matter comprising rubber and a compound possessing the structural for mula N 0H \\\C:/

where C1 and C2 are terminal carbon atoms of a chain containing only monovalent substituents which do not possess double bonds.

7. A composition of matter comprising rubber and a compound possessing the structural formula where C1 and C: are terminal carbon atoms of an unsubstituted, saturated chain.

8. A composition of matter comprising rubber and p-hydroxy N-phenyl morpholine.

9. A vulcanized rubber product resulting from the vulcanization of a composition comprising rubber, a vulcanizing agent, and a compound possessing the structural formula where C1 and C2 are terminal carbon atoms of a chain, the atoms constituting the chain containing only monovalent substituents which do not possess double bonds.

10. A vulcanized rubber product resulting from the vulcanization of a composition comprising rubber, a vulcanizing agent, an accelerator of vulcanization, and p-hydroxy N-phenyl morpholine.

ii. The method of preserving rubber which comprises treating rubber with a p-hydroxy substituted, N-aryl morpholine.

12. A composition of matter comprising rubber and an N-aryl morpholine containing a hydroxyl substituent on the aryl group.

13. A composition of matter comprising rubber and a p-hydroxy substituted, N-aryl morpholine.

14. The method of preserving rubber which comprises treating rubber with an N-hydroxyaryl morpholine.

15. The method of preserving rubber which comprises treating rubber with an N-aryl morpholine which contains a group selected from the class consisting of hydroxyl, nitroso and amino groups substituted on the aromatic nucleus. 16. The method of preserving rubber which lEl comprises treating rubber with a. compound possessing the structural formula where C1 and C2 are terminal carbon atoms of a chain, R. is an aromatic nucleus, and X is an arm'no group.

17. The method of preserving rubber which comprises treating rubber with a. compound possessing the structural formula where C1 and C2 are terminal carbon atoms of a saturated chain, the atoms constituting the chain containing only monovalent substituents which do not possess double bonds, R is an aromatic nucleus, and X is an amino group.

18. The method of preserving rubber which comprises treating rubber with an N-aryl mor pholine containing an amino group substituted on the aromatic nucleus.

19. The method of preserving rubber which comprises treating rubber with p-amino N-phenyl morpholine.

20. The method of preserving rubber which comprises treating rubber with an N-aryl morpholine containing a hydrocarbon substituted amino group in the para position.

21. The method of preserving rubber which comprises treating rubber with a p-aryiamino N-phenyl morpholine.

22. The method of preserving rubber which comprises treating rubber with p-phenylamino N-phenyl morpholine.

23. A composition of matter comprising rubber and a compound possessing the structural formula where C1 and C2 are terminal carbon atoms of a saturated chain, the atoms constituting the chain containing only monoval'ent substituents which do not possess double bonds, R. is an aromatic nucleus, and X is a hydrocarbon substituted amino group.

25. A composition of matter comprising rubber and an N-aryl morpholine containing an amino group substituted on the aromatic nucleus in the para position.

26. A composition of matter comprising rubber and p-amino N-phenyI morpholine.

27. A composition of matter comprising rubber and an N-ary1 morpholine containing a hydrocarbon substituted amino group on the aromatic nucleus. 7

28. A composition of matter comprising rubber and p-phenylamino N-phenyi morpholine.

MARION C. REED. 

